Such a material testing system has a configuration in which, for example, a pair of screw rods is supported on a table rotatably in synchronization with each other, and both end parts of a crosshead are supported by the screw rods through nuts. Also, by using rotation of a motor to rotate the pair of screw rods in synchronization with each other, the crosshead is moved along the pair of screw rods. The crosshead and the table are respectively connected with grippers. The material testing system is configured to, in a state where both ends of a test piece are gripped by the pair of grippers, move the crosshead to thereby apply test force to the test piece.
In such a material testing system, the test force acting on the test piece is detected by a load cell or the like. Also, a displacement in distance between gage marks on the test piece is measured by a displacement measuring part. Data on the displacement measured by the displacement measuring part is sampled by a sampling part, and the displacement data on the test piece is taken in together with piece of data on the test force acting on the test piece, and the like.
As the displacement measuring part, a part provided with: a video camera that photographs an image of a test piece; and an image processing circuit that, from the image of the test piece photographed by the video camera, extracts a displacement of the test piece, and outputs a measurement result of the displacement of the test piece is also used (see, for example, Patent literature 1).
A material testing system described in Patent literature 1 performs image processing of an output from the video camera provided so as to bring grippers into view, and thereby recognizes a shape of the grippers. The material testing system is also configured to move a crosshead so as to meet a distance between the grippers, which is set on the basis of information read on the basis of the shape recognition of the grippers. This eliminates the need for positioning of the grippers by manual operation in the material testing system.
Further, there is also known a material testing system in which, when an operator attaches a test piece to grippers, an auxiliary indication indicating whether the center of the test piece is aligned with a load axis of the pair of grippers is displayed, and thereby the operator can do work of making the grippers grip the test piece while seeing a monitor (see, for example, Patent literature 2).